blockcypher amount transacted larger than amount transferred [duplicate]

Question

When transferring some bitcoin from coinbase to my hardware wallet, I see on coinbase and on my hardware wallet that the amounts sent and received are about the same (minus a transaction fee), as expected. But when I look up the transaction on live.blockcypher.com, the Amount Transacted and the Input Consumed is much larger than the amount I transferred. There are two outputs, one unspent amount matching the amount I transferred minus the fee (and using my hardware wallet address) and one spent amount equal to the difference between the amount transacted and the amount I transferred (using a wallet address I don't recognize). Why is the Amount Transferred larger than the amount I actually transferred? Thank you.

Answer 1

When you create a transaction, you have to specify where the bitcoins you are spending have come from, as well as prove you are allowed to spend them. That is known as an input to the transaction. Inputs refer to outputs of previous transactions, which have not yet been spent, called UTXOs (unspent transaction outputs). Each UTXO must be spent all at once, you cannot partially spend one, when it is used as input to a transaction. Thus you will generally need to choose a UTXO which is larger than the amount you are trying to spend, and then send yourself back some change to make up the difference. That is what the second output you see is, it is the change being sent back to your wallet. See also:

• If bitcoin is indivisible, where does change come from?
• How does change work in a bitcoin transaction?
• Why does Bitcoin send the "change" to a different address?
• How is it possible to say that a bitcoin was fully spent?